Re: [PATCH] PCI: Blacklist AMD Stoney GPU devices for ATS

['Joerg Roedel']

Hi Arindam,

On Wed, Mar 29, 2017 at 07:15:42AM +0000, Nath, Arindam wrote:
> Joerg, as per my limited understanding of ATS, the ATC will respond to
> invalidation requests after making sure there are no in-flight DMA
> transactions with the address requested by IOMMU to be invalidated.
> Now since the IOMMU was sending invalidate command to GPU even though
> there was no explicit page unmapping request from the graphics
> subsystem, we _might_ end up in a situation where the ATC takes longer
> than the invalidation timeout to respond to IOMMU.

The maximum wait-time in the loop is 100ms. This should be more than
enough for the ATC to complete any in-flight transaction and flush its
internal TLB.

If that is not enough, there is almost certainly something wrong with
the hardware.



	Joerg